External topical administration is an important route for the administration of drugs in disease treatment. Many groups of drugs, including, for example, antibiotic, anti-fungal, anti-inflammatory, anesthetic, analgesic, anti-allergic, corticosteroid, retinoid and anti-proliferative medications are preferably administered in hydrophobic media, namely ointment. However, ointments often form an impermeable barrier, so that metabolic products and excreta from the wounds to which they are applied are not easily removed or drained away. Furthermore, it is difficult for the active drug dissolved in the carrier to pass through the white petrolatum barrier layer into the wound tissue, so the efficacy of the drug is reduced. In addition, ointments and creams often do not create an environment for promoting respiration of the wound tissue and it is not favorable to the normal respiration of the skin. An additional disadvantage of petroleum jelly-based products relates to the greasy feeling left following their topical application onto the skin, mucosal membranes and wounds.
A gel is a semi-rigid, jelly-like colloidal dispersion of a solid with a liquid. The main constituent of gels is liquid, e.g., water, yet they behave like solids due to the addition of a gelling agent. A hydrogel is a network of polymer chains that are water-insoluble, sometimes found as a colloidal gel in which water is the dispersion medium.
Foams are considered a more convenient vehicle for topical delivery of active agents. There are several types of topical foams, including aqueous foams, such as commonly available shaving foams; hydroalcoholic foams, emulsion-based foams, comprising oil and water components, and oleaginous foams, which consist of high oil content. Certain foams, such as shaving foams and hair mousses are not suitable as vehicles for topical drugs, because, for example, they do not absorb into the skin following application (e.g., shaving foams) or because they contain foaming surfactants that can be irritating, (e.g., ionic surfactants, in the case of shaving foam and hair mousse). “Quick-break” thermolabile foams are not ideal because they typically contain substantial amounts of alcohol, which can cause skin drying and irritation and are not convenient as they collapse quickly so that it is difficult to apply them on the target area. Also alcohol containing foams are not suitable for the treatment of open wounds and burns, neither are they suitable for treatment of body cavities, such as the vagina. On the other hand breakable foams, which remain stable on exposure to body temperature but break upon mechanical stimulation allowing easy and convenient spreading are desirable for pharmaceutical use.
Poloxamers, also known by the trade name Pluronics, are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)). Because the lengths of the polymer blocks can be customized, many different Poloxamers exist.
Compositions comprising Poloxamers are known in which Poloxamer is merely one ingredient in a complex combination of excipients with or without active pharmaceutical ingredients. Poloxamer has also been used as a constituent of foam produced by mechanical lathering without propellant.
However, most prior art foam compositions that contain Poloxamer lack stability and collapse upon contact with a delivery site in/on a subject. Some pharmaceutical compositions for rectal or vaginal administration have been developed, which comprise: (i) two or more physiologically acceptable substances each in separate parts of the composition which are such that on admixture they react to produce a physiologically acceptable gas; (ii) in at least one part of the composition a polymer stabilizer which is adapted to facilitate the formation of a water-soluble collapsible foam structure; and (iii) in at least one part of the composition a pharmaceutically active substance. These compositions must be delivered using multi-compartment syringes and rely on there being a chemical reaction between parts i) and ii). In the example xanthan and Poloxamer are in combination, wherein the concentration of poloxamer is less than 0.2% and xanthan gum is present in a five fold higher concentration than Poloxamer.
Foam compositions for rectal administration of a solid powder in which the surfactant is Poloxamer have been published. Such compositions include (a) over 25 wt % of a powdered active principle, and (b) 1-20 wt % of a surfactant, and the balance (c) being water. The powdered active principle has a particle size of less than 20 μm.
Also published are compositions of matter without fatty alcohol where the surfactant may be Poloxamer but in the Poloxamer examples the concentration of Poloxamer is 1.6% and a high level of ethyl alcohol (60%) is used to form a foamable delivery system.
A composition has been disclosed comprising (a) monohydric alcohol (b) surfactant comprising a dimethicone surfactant and (c) a builder to improve or provide stability of a foam derived from the composition, in which the builder can be a Poloxamer and wherein the alcohol is 35% to 99.5%. In the examples the Poloxamer foam builder was 0.08% and 0.3% and the alcohol was 65% ethanol 200% proof.
Sprayable germicidal foam compositions to cover wounded skin containing Poloxamer which remain stable for at least an hour and have a half life of 5-7 hours are known. Fatty acids and fatty alcohols are required and the Poloxamer must not exceed 3× the fatty acids or be less than half their combined amount. In the examples Poloxamer was 1.5% to less than 2%.
Foamable suspension gel formulations containing benzyl peroxide in combination with clindamycin have been published in which the gel base contains 0.1 to 2% of a thickening agent. In the Examples, the thickening agent is 1% xantham gum, and it is used with a dispensing or wetting agent (1% Poloxamer 188 and other components), with water being the main component. Although other agents are listed as dispersing or wetting agents only Poloxamer 188 is used in the examples. Good wetting agents are typically considered to be poor foaming agents and vice versa.
Liquid bioadhesive microemulsions or liopsomic dispersions containing proteinic substances are described in which the composition contains a fixing copolymer. At body temperature the viscosity of the compositions is increased and provides an increased residence time at the administration site.
A composition for a foam and a process for preparing have been disclosed in the art, the composition including by weight (a) more than 25% of an active ingredient in powder form; (b) from 1% to 20% of a surfactant; the balance being composed of water, wherein the powder of the active ingredient has a particle size below 20 μm. The surfactant can be a mixture of two surfactants one being a hydrophilic surfactant with a HLB greater than 10 and the other being a polyoxyalkylene-based surfactant (possibly, Poloxamer). In the examples, the amount of hydrophilic surfactant is much greater than the Poloxamer.
The use of Poloxamers with ability to change the sol-gel transition temperature by pH adjustment and by ionic strength adjustment has been disclosed. The preferred polymers are those which form gels at a concentration range of 10% to 50% of the polymer to water.
The use of thermosetting copolymers (Pluronic 127 or Lutrol127) with liposomic dispersions to administer a peptide or protein drug to a body surface is known. In the examples 13%-19.5% copolymers were used.
Other prior art complex compositions include formulations comprising a polymeric agent, which may be a phase change polymer, which alters the composition behavior from fluid-like prior to administration to solid-like upon contact with the target mucosal surface. Such phase change results from external stimuli, such as changes in temperature or pH and exposure to specific ions (e.g., Ca2+). Non-limiting examples of phase change polymers include poly(N-isopropylamide), and Poloxamer 407®. High concentrations of Poloxamer are used for gelling.
There are disclosed new, improved, convenient to use, stable foam Poloxamer carrier formulations and pharmaceutical compositions, which are an advance over the prior art.
Foams are complex dispersion systems which do not form under all circumstances. Slight shifts in foam composition, such as by the addition of active ingredients, may destabilize the foam. Foams are very complex and sensitive systems and are not formed at will. Mere addition of basic ingredients like oil, surfactant and propellant is far from sufficient to produce foams of quality that are homogenous, stable, breakable upon mechanical force and can be used to provide a shelf stable pharmaceutical or cosmetic composition. Small deviations may lead to foam collapse. Much consideration needs to be given to facilitate the introduction of an active agent, such as examining compatibility and non reactivity with the various excipients and container and determining shelf life chemical and physical stability.
Neubourg (US 2006/0099151), for example, notes that the stability of foam is strongly dependent on the specific composition of the foam forming components, so that even small deviations in the composition may lead to a collapse of the foam. Gordon et al. (U.S. Pat. No. 3,456,052). also teaches that one cannot generate a good quality foam by simply adding a propellant to a mixture of components:
The term “foam” is a general term that encompasses a range of substances. Accordingly, the context in which “foam” is discussed must be examined carefully. The type and quality of the foam is of critical importance. There are many different types of foams and within each foam type there are many levels of qualities. For example, the froth on the head of beer, lather of shampoo, and lather of shaving cream have been loosely described as foam but all are different from one another. At one end of the cosmetic or pharmaceutical foam spectrum the foam can be long lasting and essentially not readily breakable like shaving foams. At the other end of the spectrum the foam can be quick breaking and collapses upon release.
Thermolabile foams are an example of type of quick breaking foam. They can contain significant amounts of thermolabile substances that aid their collapse upon being exposed to an increased temperature for example when applied to a body surface at 37 C. Upon being exposed to the higher temperature they collapse rapidly. Examples are foam formulations that comprise significant amounts of volatile solvents.
Breakable foam is a specialized type of foam. It is a low density foam that is stable on release at least in the short time span of several minutes, which facilitates application to a target area; but can break readily upon the application of shear force such as gentle rubbing to spread easily over a target surface. It is not thermolabile (and does not melt at skin temperature) and nor does it display late or long delayed expansion over minutes.
Some foams expand slowly whilst others do so quickly. Some foams foam immediately and some demonstrate delayed foaming. Some require mechanical lathering and some expulsion by propellant. Whilst they all fall under the so called term “foam” and may appear to have some common ingredients the results and properties of these products are different.
A suitable foamable formulation for a particular application may present challenges at several levels. For example, a foam formulation may require a stable pre foam formulation; a stable pre foam propellant formulation and ultimately delivery an effective measured amount of active agent to a target. Each of these objectives poses its own unique challenges.
The pharmaceutical and cosmetic foams discussed herein are generated in general terms by manufacturing a suitable foamable carrier composition and loading the carrier in a pressurized valved canister with an appropriate propellant. Upon expelling the canister contents a foam can be released. The type, nature and quality of the foam depends inter alia on the carrier composition, the active agent, the propellant and the method of manufacture and storage. Making a stable (physically and chemically) formulation that can be stored in a canister with a propellant that remains stable and can produce a breakable foam of quality on release is far from trivial.
An additional difficulty frequently encountered with propellant foams is their inability to dispense a satisfactorily uniform application of the medically active ingredient throughout the use of the aerosol container. This is particularly due to the fact that the active material is not stably dispersed in the foamable composition so that it will have a tendency to settle to the bottom. Further, the dispersed material will sometimes clog the spray dispensing valve to further interfere with the uniform dispensing of the medicament. Issues such as the effect of the propellant on the properties of the formulation such as viscosity and miscibility can be critical; whilst the pressure of the propellant; and the shakability of the pre foam formulation with propellant can also effect the ability to achieve satisfactory uniform application as well as the ability to avoid jets and tailing.